I know but I'm a php noob.
Revenue Loop runs on Directtrack. So its the same sysem as Ads4Dough, Copeac, CPA Empire. WSDL is very easy just read a couple of simple tutorials and start playing around with it and you'll have it in no time.
Well CURL would probably be a good start.
Use CURL to call the API then use your favorite parsing method to get the data you want out of the result.